Fix Arc::clone()'s MAX_REFCOUNT check (off-by-one)
Before, the strong count of an `Arc` could be set to
`MAX_REFCOUNT + 1`, because when this happened, `old_size` would
be exactly `MAX_REFCOUNT`. `Arc::clone()` would not abort.
This commit changes the check in `Arc::clone()` to also abort if
the old value is equal to `MAX_REFCOUNT`, because then the new
value will be equal to `MAX_REFCOUNT + 1`.
A test would require allocating memory for `isize::MAX` pointers.
This would probably crash any machine, so no test is submitted
with this commit.
There is a *little* code duplication, but primarily for sake of "match
exhaustiveness". Let's blame Linux/MIPS for not exposing endianness
explicitly in `uname -m` (that's user-space interface and as such is
frozen).
Currently the build won't work as we have to wait for a new stage0 for
the MIPS host compilers, but this paves the way to self-hosted Rust on
MIPS. The cross-compiled MIPS binaries are confirmed to work on the
Loongson 3A2000 (MIPS64r2-compatible) so we have plenty of confidence
that they'll work on other MIPS platforms too, as Linux/MIPS user-space
ABI is consistent across machines of the same bitness.
The `mipsel` `target_arch` was introduced with the initial MIPSel
support (rust-lang/rust@82ec1aef29),
but was subsequently removed with implementation of the Flexible Target
Specification (Rust RFC 0131,
rust-lang/rust@3a8f4ec32a).
This is the only remaining instance in rustc. All others are in the libc
repo, and are fixed in rust-lang/libc@b3676593f6.
macros: improve shadowing checks
This PR improves macro-expanded shadowing checks to work with out-of-(pre)order expansion.
Out-of-order expansion became possible in #37084, so this technically a [breaking-change] for nightly.
The regression test from this PR is an example of code that would break.
r? @nrc
Force static linking of LLVM
Run `llvm-config` with `--link-static` if available, to force static linking of LLVM.
This option was added in LLVM 3.8.
This is my first pull request, any feedback is welcome!
Fixes#36854
See also: #36996
The constant name `MAX_REFCOUNT` suggests that the value is a
_hard_ limit on the amount of references to an `Arc`. This is
a more soft limit however. This commit adds a comment to the
constant to annotate this.
See also: PR #37605
[4/n] rustc: harden against InferOk having obligations in more cases.
_This is part of a series ([prev](https://github.com/rust-lang/rust/pull/37402) | [next](https://github.com/rust-lang/rust/pull/37408)) of patches designed to rework rustc into an out-of-order on-demand pipeline model for both better feature support (e.g. [MIR-based](https://github.com/solson/miri) early constant evaluation) and incremental execution of compiler passes (e.g. type-checking), with beneficial consequences to IDE support as well.
If any motivation is unclear, please ask for additional PR description clarifications or code comments._
<hr>
This adds more asserts that `InferOk` results have no obligations, pending completion of #32730.
Each of these could accidentally drop obligations on the floor if they start getting produced by unification, and a future change does just that, in order to produce a "shallow success" (hopefully leading to ambiguities during trait selection), _without_ the possibility of an eventual success - mostly guarded by ICEs for now.
Add example using Self to reference
When I first came across `Self` I had a hard time finding references to it in the docs (and it's also been asked about on [StackOverflow](http://stackoverflow.com/questions/32304595/whats-the-difference-between-self-and-self).
I hope this example provides someone who comes across it for the first time a little more help. If there is a better way to show an example actually using `Self`, I'm happy to modify this. It was just the simplest place to start I could see.
std: Track change to cprng syscall signature (Fuchsia)
The mx_cprng_draw syscall has changed signature to separate the status
and size return values, rather than multiplexing them into a single
value with errors interpreted as a negative value. This patch tracks
that change.
Fix issues with the Add/AddAssign impls for Cow<str>
* Correct the stability attributes.
* Make Add and AddAssign actually behave the same.
* Use String::with_capacity when allocating a new string.
* Fix the tests.
Fix ICE when querying DefId on Def::Err.
Also moves computations into check that `kind_id` is `Ok(_)`, which is in theory an optimization, though I expect it's minor.
Fixes#37534.
r? @eddyb.
set frame pointer elimination attribute for main
The rustc-generated function `main` should respect the same config for
frame pointer elimination as the rest of code.
rustc: Add knowledge of Windows subsystems.
This commit is an implementation of [RFC 1665] which adds support for the
`#![windows_subsystem]` attribute. This attribute allows specifying either the
"windows" or "console" subsystems on Windows to the linker.
[RFC 1665]: https://github.com/rust-lang/rfcs/blob/master/text/1665-windows-subsystem.md
Previously all Rust executables were compiled as the "console" subsystem which
meant that if you wanted a graphical application it would erroneously pop up a
console whenever opened. When compiling an application, however, this is
undesired behavior and the "windows" subsystem is used instead to have control
over user interactions.
This attribute is validated, but ignored on all non-Windows platforms.
cc #37499
Reduce the number of bytes hashed by IchHasher.
IchHasher uses blake2b hashing, which is expensive, so the fewer bytes hashed
the better. There are two big ways to reduce the number of bytes hashed.
- Filenames in spans account for ~66% of all bytes (for builds with debuginfo).
The vast majority of spans have the same filename for the start of the span
and the end of the span, so hashing the filename just once in those cases is
a big win.
- u32 and u64 and usize values account for ~25%--33% of all bytes (for builds
with debuginfo). The vast majority of these are small, i.e. fit in a u8, so
shrinking them down before hashing is also a big win.
This PR implements these two optimizations. I'm certain the first one is safe.
I'm about 90% sure that the second one is safe.
Here are measurements of the number of bytes hashed when doing
debuginfo-enabled builds of stdlib and
rustc-benchmarks/syntex-0.42.2-incr-clean.
```
stdlib syntex-incr
------ -----------
original 156,781,386 255,095,596
half-SawSpan 106,744,403 176,345,419
short-ints 45,890,534 118,014,227
no-SawSpan[*] 6,831,874 45,875,714
[*] don't hash the SawSpan at all. Not part of this PR, just implemented for
comparison's sake.
```
For debug builds of syntex-0.42.2-incr-clean, the two changes give a 1--2%
speed-up.
